Polyphase ac motor and winding switching system

Abstract

A polyphase AC motor comprises: a plurality of first partial windings respectively wound around a plurality of teeth; and a plurality of second partial windings respectively wound around the plurality of teeth. The first partial windings and the second partial windings wound around the same teeth are connected in parallel.

Description

Multiphase AC motor and winding switching system

[0001] This disclosure relates to a polyphase AC motor and a winding switching system. This application claims priority to Japanese Application No. 2024-124551, filed on July 31, 2024, and incorporates the entire content of said Japanese application by reference.

[0002] For example, some motors mounted on electric vehicles are capable of switching between a low-speed, high-torque operating state and a high-speed, low-torque operating state by switching the connection of multiple windings. Patent Document 1 discloses a device that switches the connection state of the four windings of each phase of a permanent magnet synchronous motor between a state in which all four windings are connected in series, a state in which all four windings are connected in parallel, and a state in which two windings connected in parallel and two windings connected in parallel are connected in series.

[0003] International Publication No. 2016 / 051456

[0004] A polyphase AC motor according to one aspect of the present disclosure comprises a plurality of first partial windings wound around each of a plurality of teeth, and a plurality of second partial windings wound around each of the plurality of teeth, and the first partial windings and the second partial windings wound around the same teeth are connected in parallel.

[0005] FIG. 1 is a diagram showing an example of the configuration of a winding switching system according to a first embodiment. FIG. 2 is a cross-sectional view showing an example of the configuration of a three-phase AC motor according to the first embodiment. FIG. 3 is a circuit diagram showing an example of the configuration of a winding switching device according to the first embodiment. FIG. 4A is a diagram for explaining an example of a first connection state of windings in the motor according to the first embodiment. FIG. 4B is a diagram for explaining an example of a second connection state of windings in the motor according to the first embodiment. FIG. 5 is a circuit diagram showing an example of the connection relationship of a U-phase winding in the motor according to the first embodiment. FIG. 6 is a circuit diagram showing an example of the configuration of a winding switching device according to a second embodiment. FIG. 7A is a diagram for explaining an example of a first connection state of windings in the motor according to the second embodiment. FIG. 7B is a diagram for explaining an example of a second connection state of windings in the motor according to the second embodiment. FIG. 8 is a circuit diagram showing an example of the connection relationship of a U-phase winding in the motor according to the second embodiment.

[0006] In fractional slot motors, such as 10 poles and 12 slots or 8 poles and 9 slots, there are in-phase slots with different phases. Since the induced voltage phases of the windings in the in-phase slots are different from each other, they cannot be connected in parallel.

[0007] According to the present disclosure, regardless of the number of poles and the number of slots, it is possible to configure a motor having characteristics similar to a motor in which windings in the same phase slots are connected in parallel.

[0008] The following provides an outline of embodiments of the present disclosure.

[0009] (1) A polyphase AC motor according to this embodiment includes a plurality of first partial windings wound around a plurality of teeth, respectively, and a plurality of second partial windings wound around the plurality of teeth, the first partial windings and the second partial windings wound around the same tooth being connected in parallel. The phase difference between the magnetic field formed by the first partial windings and the magnetic field formed by the rotor is the same as the phase difference between the magnetic field formed by the second partial windings wound around the same tooth as the first partial windings and the magnetic field formed by the rotor. In other words, the phases of the induced voltages generated in the first partial windings and the second partial windings wound around the same tooth are the same. Therefore, the first partial windings and the second partial windings wound around the same tooth can be connected in parallel, and a motor with one winding per slot can be configured with characteristics similar to those of a motor with windings in the same phase slots connected in parallel.

[0010] (2) In the above (1), a first series circuit in which the first partial winding wound on a first tooth and the first partial winding wound on a second tooth are connected in series, and a second series circuit in which the second partial winding wound on the first tooth and the second partial winding wound on the second tooth are connected in series, may be connected in parallel in the same phase. By connecting the first series circuit and the second series circuit in parallel, it is possible to obtain characteristics similar to those obtained when windings in different slots are connected in parallel in a motor having one winding per slot.

[0011] (3) In the above (2), a third series circuit in which the first partial winding wound on a third tooth and the first partial winding wound on a fourth tooth are connected in series, and a fourth series circuit in which the second partial winding wound on the third tooth and the second partial winding wound on the fourth tooth are connected in series may be connected in parallel in the same phase as the first series circuit and the second series circuit. By connecting the third series circuit and the fourth series circuit in parallel, it is possible to obtain characteristics similar to those obtained when windings in different slots are connected in parallel in a motor having one winding per slot.

[0012] (4) In the above (3), the polyphase AC motor may be capable of connecting the first series circuit, the second series circuit, the third series circuit, and the fourth series circuit in parallel, thereby making it possible to obtain characteristics in a motor having one winding per slot that are similar to those obtained when two windings connected in parallel and two windings connected in parallel are connected in series.

[0013] (5) In the above (4), the polyphase AC motor may be configured to be switchable between a first connection state in which a first circuit in which the first series circuit and the second series circuit are connected in parallel and a second circuit in which the third series circuit and the fourth series circuit are connected in parallel are connected in series, and a second connection state in which the first circuit and the second circuit are connected in parallel. This makes it possible to configure a motor in which, in a motor provided with one winding per slot, the motor can be switched between a first connection state having characteristics approximating a state in which two windings connected in parallel and two windings connected in parallel are connected in series, and a second connection state having characteristics approximating a state in which all four windings are connected in parallel.

[0014] (6) In the above (1), a first parallel circuit in which the first partial winding wound on a first tooth and the second partial winding wound on the first tooth are connected in parallel, and a second parallel circuit in which the first partial winding wound on a second tooth and the second partial winding wound on the second tooth are connected in parallel may be connected in series in the same phase. By connecting the first parallel circuit and the second parallel circuit in series, it is possible to obtain characteristics similar to those obtained when windings in different slots are connected in parallel in a motor having one winding per slot.

[0015] (7) In the above (6), a third parallel circuit in which the first partial winding wound on a third tooth and the second partial winding wound on the third tooth are connected in parallel, and a fourth parallel circuit in which the first partial winding wound on a fourth tooth and the second partial winding wound on the fourth tooth are connected in parallel may be connected in series in the same phase as the first parallel circuit and the second parallel circuit. By connecting the third parallel circuit and the fourth parallel circuit in series, it is possible to obtain characteristics similar to those obtained when windings in different slots are connected in parallel in a motor having one winding per slot.

[0016] (8) In the above (7), the polyphase AC motor may be capable of connecting the first parallel circuit, the second parallel circuit, the third parallel circuit, and the fourth parallel circuit in series, thereby making it possible to obtain characteristics similar to those obtained when two windings connected in parallel and two windings connected in parallel are connected in series in a motor having one winding per slot.

[0017] (9) In the above (8), the polyphase AC motor may be configured to be switchable between a third connection state in which a third circuit in which the first parallel circuit and the second parallel circuit are connected in series, a fourth circuit in which the third parallel circuit and the fourth parallel circuit are connected in series, and a fourth connection state in which the third circuit and the fourth circuit are connected in parallel. This makes it possible to configure a motor in which, in a motor having one winding per slot, the motor can be switched between the third connection state, which has characteristics approximating a state in which two windings connected in parallel and two windings connected in parallel are connected in series, and the fourth connection state, which has characteristics approximating a state in which all four windings are connected in parallel.

[0018] (10) In any one of (2) to (9) above, a first phase difference between a first stator magnetic field formed by the first partial winding and the second partial winding wound around the first teeth, respectively, and a rotor magnetic field formed by the rotor may be different from a second phase difference between a second stator magnetic field formed by the first partial winding and the second partial winding wound around the second teeth, respectively, and the rotor magnetic field formed by the rotor. This makes it possible to obtain characteristics similar to those obtained when windings in different slots are connected in parallel in a motor having one winding per slot, even though the phases of the induced voltages in the slots of the first teeth and the second teeth are different.

[0019] (11) In the above (10), a third phase difference between a third stator magnetic field formed by the first partial winding and the second partial winding wound around a third tooth and a rotor magnetic field formed by the rotor may be different from a fourth phase difference between a fourth stator magnetic field formed by the first partial winding and the second partial winding wound around a fourth tooth and a rotor magnetic field formed by the rotor. This makes it possible to obtain characteristics similar to those obtained when windings in different slots are connected in parallel in a motor having one winding per slot, even though the induced voltage phases in the slots of the third teeth and the fourth teeth are different.

[0020] (12) In the above (11), the first phase difference and the third phase difference may be the same, and the second phase difference and the fourth phase difference may be the same. This allows a motor with one winding per slot to obtain characteristics similar to those obtained when windings in different slots are connected in parallel, even if the induced voltage phases in the slots of the first teeth and the second teeth are different and the induced voltage phases in the slots of the third teeth and the fourth teeth are different.

[0021] (13) A winding switching system according to this embodiment includes a polyphase AC motor capable of switching the connection state of multiple windings between a first connection state and a second connection state, a power converter that converts power output from a power source into AC power and supplies the AC power to the AC motor, and a winding switching device that switches the connection state of the multiple windings, wherein the polyphase AC motor includes multiple first partial windings wound around multiple teeth, respectively, and multiple second partial windings wound around the multiple teeth, respectively, and the first partial windings and the second partial windings wound around the same tooth are connected in parallel. The phase difference of the magnetic field formed by the first partial windings relative to the magnetic field formed by the rotor is the same as the phase difference of the magnetic field formed by the second partial winding wound around the same tooth as the first partial windings relative to the magnetic field formed by the rotor. That is, the phases of the induced voltages generated in the first partial winding and the second partial winding wound around the same tooth are the same. Therefore, the first partial winding and the second partial winding wound on the same tooth can be connected in parallel, and in a motor having one winding per slot, it is possible to construct a motor having characteristics similar to those of windings in the same phase slots connected in parallel.

[0022] The present disclosure can be realized not only as a polyphase AC motor having the above-described characteristic configuration, and a winding switching system including a polyphase AC motor, but also as a control device that switches the winding connection state of a polyphase AC motor, a control method that switches the winding connection state of a polyphase AC motor, a control program for switching the winding connection state of a polyphase AC motor, and a semiconductor integrated circuit that realizes part or all of the control device.

[0023] Hereinafter, details of embodiments of the present disclosure will be described with reference to the drawings. Note that at least some of the embodiments described below may be combined in any manner.

[0024] [1. First Embodiment] [1-1. Winding Switching System] FIG. 1 is a diagram showing an example of the configuration of a winding switching system according to a first embodiment.

[0025] The winding switching system 10 is mounted on a vehicle (hereinafter referred to as an "electric vehicle") that is propelled by a motor, such as an electric vehicle, a plug-in hybrid vehicle, etc. The winding switching system 10 includes a motor 20, a power converter 30, a battery 40, a control device 50, and a winding switching device 100.

[0026] The motor 20 is a driving motor that generates propulsion power for the electric vehicle. The motor 20 is a three-phase AC motor that is driven by three-phase AC power. An example of the motor 20 is a permanent magnet synchronous motor.

[0027] The battery 40 is a battery that supplies power to drive the motor 20. The battery 40 is a secondary battery, such as a lithium ion battery.

[0028] The power converter 30 is an inverter that converts DC power supplied from the battery 40 into three-phase AC power. The power converter 30 may have a function of converting three-phase AC power output when the motor 20 functions as a generator into DC power and charging the battery 40.

[0029] The power converter 30 includes U-phase, V-phase, and W-phase legs. The U-phase leg includes switches 31u and 32u, the V-phase leg includes switches 31v and 32v, and the W-phase leg includes switches 31w and 32w. The switches 31u, 32u, 31v, 32v, 31w, and 32w perform switching to convert DC power into three-phase AC power. The switches 31u, 32u, 31v, 32v, 31w, and 32w are, for example, insulated gate bipolar transistors (IGBTs) or power metal oxide semiconductor field-effect transistors (MOSFETs).

[0030] A power line 35u corresponding to the U phase extends from the U-phase leg, a power line 35v corresponding to the V phase extends from the V-phase leg, and a power line 35w corresponding to the W phase extends from the W-phase leg. In the power converter 30, a current sensor 33u is provided on the power line 35u, a current sensor 33v is provided on the power line 35v, and a current sensor 33w is provided on the power line 35w. The current sensor 33u detects the current value of the U-phase current Iu. The current sensor 33v detects the current value of the V-phase current Iv. The current sensor 33w detects the current value of the W-phase current Iw. The current sensors 33u, 33v, and 33w can detect the current values ​​of the currents Iu, Iv, and Iw flowing through the power lines 35u, 35v, and 35w, including DC and AC components. The current sensors 33u, 33v, and 33w are, for example, DCCTs (direct current transformers) or shunt resistors.

[0031] The winding switching device 100 is disposed between the motor 20 and the power converter 30. However, the position of the winding switching device 100 is not limited to between the motor 20 and the power converter 30. The power converter 30 and the winding switching device 100 are connected by power lines 35u, 35v, and 35w, and the winding switching device 100 and the motor 20 are connected by a plurality of power lines 25. The winding switching device 100 switches the connection state of a plurality of windings of the motor 20. The configuration of the winding switching device 100 will be described later. Three-phase AC currents Iu, Iv, and Iw output from the power converter 30 are supplied to the motor 20 via the winding switching device 100.

[0032] The control device 50 controls the power converter 30 and the winding switching device 100. Specifically, signal lines extend from the control device 50 to each of the switches 31u, 32u, 31v, 32v, 31w, and 32w, and the control device 50 controls the on / off timing of the switches 31u, 32u, 31v, 32v, 31w, and 32w. A signal line extends from the control device 50 to the winding switching device 100, and the control device 50 outputs a switching command signal to the winding switching device 100 to command the switching of the connection state of the windings.

[0033] 2 is a cross-sectional view showing an example of the configuration of the three-phase AC motor according to the first embodiment. Fig. 2 shows a cross section perpendicular to the central axis.

[0034] The motor 20 includes a stator 210 and a rotor 220 .

[0035] The stator 210 is made of a soft magnetic material and includes a cylindrical yoke 210Y and a plurality of teeth 210Tu1, 210Tu2, 210Tv1, 210Tv2, 210Tw1, 210Tw2, 210Tu3, 210Tu4, 210Tv3, 210Tv4, 210Tw3, and 210Tw4 arranged on the inner periphery of the yoke. Hereinafter, the teeth 210Tu1, 210Tu2, 210Tv1, 210Tv2, 210Tw1, 210Tw2, 210Tu3, 210Tu4, 210Tv3, 210Tv4, 210Tw3, and 210Tw4 will be collectively referred to as "teeth 210T."

[0036] Each of the teeth 210T is a protrusion extending from the inner peripheral surface of the yoke 210Y toward the center. The teeth 210T are arranged at equal intervals in the circumferential direction around the central axis O of the motor 20.

[0037] Each of the multiple teeth 210T corresponds to one of the U-phase, V-phase, and W-phase. A winding is wound around each tooth 210T. The winding wound around one tooth forms a slot. In other words, the number of slots is the same as the number of teeth. In the example shown in FIG. 2, the number of slots is 12.

[0038] In the motor 20 according to the present disclosure, the winding is divided in each slot. That is, a first partial winding and a second partial winding are wound around each tooth 210T. The first partial winding and the second partial winding wound around the tooth 210T corresponding to the U-phase correspond to the U-phase. The first partial winding and the second partial winding wound around the tooth 210T corresponding to the V-phase correspond to the V-phase. The first partial winding and the second partial winding wound around the tooth 210T corresponding to the W-phase correspond to the W-phase.

[0039] Specifically, the first partial windings 21u1, 21u2, 21u3, and 21u4 and the second partial windings 22u1, 22u2, 22u3, and 22u4 corresponding to the U phase are wound around the teeth 210Tu1, 210Tu2, 210Tu3, and 210Tu4 corresponding to the U phase, respectively. Here, elements having the common reference numerals "u1," "u2," "u3," and "u4" correspond to one another. That is, for example, the first partial winding 21u1 and the second partial winding 22u1 are wound around the tooth 210Tu1. The first partial winding 21u2 and the second partial winding 22u2 are wound around the tooth 210Tu2. The first partial winding 21u3 and the second partial winding 22u3 are wound around the tooth 210Tu3. The first partial winding 21u4 and the second partial winding 22u4 are wound around the tooth 210Tu4. That is, the U-phase slot Su1 includes the first partial winding 21u1 and the second partial winding 22u1. The U-phase slot Su2 includes the first partial winding 21u2 and the second partial winding 22u2. The U-phase slot Su3 includes the first partial winding 21u3 and the second partial winding 22u3. The U-phase slot Su4 includes the first partial winding 21u4 and the second partial winding 22u4.

[0040] Similarly, the first partial windings 21v1, 21v2, 21v3, and 21v4 and the second partial windings 22v1, 22v2, 22v3, and 22v4 corresponding to the V phase are wound around the teeth 210Tv1, 210Tv2, 210Tv3, and 210Tv4 corresponding to the V phase, respectively. That is, the V-phase slot Sv1 includes the first partial winding 21v1 and the second partial winding 22v1. The V-phase slot Sv2 includes the first partial winding 21v2 and the second partial winding 22v2. The V-phase slot Sv3 includes the first partial winding 21v3 and the second partial winding 22v3. The V-phase slot Sv4 includes the first partial winding 21v4 and the second partial winding 22v4. The first partial windings 21w1, 21w2, 21w3, 21w4 and the second partial windings 22w1, 22w2, 22w3, 22w4 corresponding to the W phase are wound around the teeth 210Tw1, 210Tw2, 210Tw3, 210Tw4 corresponding to the W phase, respectively. That is, the W-phase slot Sw1 includes the first partial winding 21w1 and the second partial winding 22w1. The W-phase slot Sw2 includes the first partial winding 21w2 and the second partial winding 22w2. The W-phase slot Sw3 includes the first partial winding 21w3 and the second partial winding 22w3. The W-phase slot Sw4 includes the first partial winding 21w4 and the second partial winding 22w4.

[0041] In the motor 20 according to the first embodiment, the two slots Su1 and Su2 in the U phase are adjacent to each other, and the two slots Su3 and Su4 in the U phase are adjacent to each other. The slots Su1 and Su3 in the U phase are spaced 180° apart, and the slots Su2 and Su4 are spaced 180° apart. The two slots Sv1 and Sv2 in the V phase are adjacent to each other, and the two slots Sv3 and Sv4 in the V phase are adjacent to each other. The slots Sv1 and Sv3 in the V phase are spaced 180° apart, and the slots Sv2 and Sv4 are spaced 180° apart. The two slots Sw1 and Sw2 in the W phase are adjacent to each other, and the two slots Sw3 and Sw4 in the W phase are adjacent to each other. The W-phase slots Sw1 and Sw3 are spaced apart by 180°, and the slots Sw2 and Sw4 are spaced apart by 180°. Specifically, the slots Su1, Su2, Sv1, Sv2, Sw1, Sw2, Su3, Su4, Sv3, Sv4, Sw3, and Sw4 are arranged in this order in the counterclockwise direction in FIG.

[0042] The rotor 220 includes a plurality of permanent magnets 220M. The plurality of permanent magnets 220M are arranged in an annular shape in the circumferential direction of the central axis O. More specifically, each permanent magnet 220M has an elongated plate shape. Adjacent pairs of permanent magnets 220M are arranged in a V-shape when viewed in the direction of the central axis O, and each pair of permanent magnets 220M is arranged in an annular shape so that the tip of the V faces the center O. In other words, each permanent magnet 220M is inclined with respect to the radial direction so that a first end of the permanent magnet 220M is away from the center O and a second end is closer to the center O.

[0043] For example, a first end of the permanent magnet 220M that is farther from the central axis O is an S pole, and a second end that is closer to the central axis O is an N pole. In other words, the ends of adjacent permanent magnets 220M that are close to each other have the same polarity. The first ends of a pair of adjacent permanent magnets 220M whose first ends are close to each other form an S pole, and the second ends of a pair of adjacent permanent magnets 220M whose second ends are close to each other form an N pole.

[0044] The number of permanent magnets 220M shown in Fig. 2 is 20. Therefore, the 20 permanent magnets 220M form 10 south poles and 10 north poles. In other words, the number of poles of the motor 20 shown in Fig. 2 is 10. Therefore, the motor 20 is a 10-pole, 12-slot three-phase AC permanent magnet synchronous motor.

[0045] For example, in the case of a three-phase AC permanent magnet synchronous motor with a pole-to-slot ratio of 2:3, such as 8 poles and 12 slots or 6 poles and 9 slots, the mechanical angle and electrical angle are the same. Therefore, by grouping one slot for each of the U, V, and W phases and arranging these groups circumferentially in the order of U, V, and W, such as UVWUVW..., it is possible to easily align the induced voltage phases of slots of the same phase. On the other hand, motor 20 is a so-called fractional slot motor, which does not have a 2:3 pole-to-slot ratio. In a fractional slot motor, there are slots of the same phase whose induced voltage phases do not match.

[0046] 2, the induced voltage phases match between a pair of slots Su1 and Su3 spaced 180° apart, and the induced voltage phases match between a pair of slots Su2 and Su4 spaced 180° apart. On the other hand, the induced voltage phases do not match between a pair of adjacent slots Su1 and Su2, and the induced voltage phases do not match between a pair of adjacent slots Su3 and Su4.

[0047] 3 is a circuit diagram showing an example of the configuration of the winding switching device according to the first embodiment. As described above, the first partial windings 21u1, 21u2, 21u3, and 21u4 and the second partial windings 22u1, 22u2, 22u3, and 22u4 correspond to the U-phase, the first partial windings 21v1, 21v2, 21v3, and 21v4 and the second partial windings 22v1, 22v2, 22v3, and 22v4 correspond to the V-phase, and the first partial windings 21w1, 21w2, 21w3, and 21w4 and the second partial windings 22w1, 22w2, 22w3, and 22w4 correspond to the W-phase. However, the number of partial windings in each slot is not limited to two and may be three or more.

[0048] In the motor 20 according to the first embodiment, the phases of the induced voltages applied to the first and second partial windings in the same slot are the same. Therefore, in the first embodiment, the first and second partial windings in the same slot are connected in parallel. Specifically, the first and second partial windings 21u1 and 22u1 in the slot Su1 are connected in parallel. The same applies to the other slots Su2, Sv1, Sv2, Sw1, Sw2, Su3, Su4, Sv3, Sv4, Sw3, and Sw4.

[0049] A series circuit (first series circuit) made up of the first partial winding 21u1 in the slot Su1 and the first partial winding 21u2 in the slot Su2 adjacent to the slot Su1, and a series circuit (second series circuit) made up of the second partial winding 22u1 in the slot Su1 and the second partial winding 22u2 in the slot Su2 are connected in parallel to form a circuit Cu1 (first circuit).

[0050] A series circuit (third series circuit) consisting of the first partial winding 21u3 in slot Su3 and the first partial winding 21u4 in slot Su4 adjacent to slot Su3, and a series circuit (fourth series circuit) consisting of the second partial winding 22u3 in slot Su3 and the second partial winding 22u4 in slot Su4 are connected in parallel to form circuit Cu2 (first circuit).

[0051] A series circuit (first series circuit) consisting of the first partial winding 21v1 in slot Sv1 and the first partial winding 21v2 in slot Sv2 adjacent to slot Sv1, and a series circuit (second series circuit) consisting of the second partial winding 22v1 in slot Sv1 and the second partial winding 22v2 in slot Sv2 are connected in parallel to form circuit Cv1 (first circuit).

[0052] A series circuit (third series circuit) of the first partial winding 21v3 in slot Sv3 and the first partial winding 21v4 in slot Sv4 adjacent to slot Sv3, and a series circuit (fourth series circuit) of the second partial winding 22v3 in slot Sv3 and the second partial winding 22v4 in slot Sv4 are connected in parallel to form circuit Cv2 (first circuit).

[0053] A series circuit (first series circuit) consisting of the first partial winding 21w1 in slot Sw1 and the first partial winding 21w2 in slot Sw2 adjacent to slot Sw1, and a series circuit (second series circuit) consisting of the second partial winding 22w1 in slot Sw1 and the second partial winding 22w2 in slot Sw2 are connected in parallel to form a circuit Cw1 (first circuit).

[0054] A series circuit (third series circuit) consisting of the first partial winding 21w3 in slot Sw3 and the first partial winding 21w4 in slot Sw4 adjacent to slot Sw3, and a series circuit (fourth series circuit) consisting of the second partial winding 22w3 in slot Sw3 and the second partial winding 22w4 in slot Sw4 are connected in parallel to form circuit Cw2 (first circuit).

[0055] A first end of the circuit Cu1 (a connection point between the first partial winding 21u1 and the second partial winding 22u1) is connected to the power line 35u, and a second end of the circuit Cu1 (a connection point between the first partial winding 21u2 and the second partial winding 22u2) is connected to the power line 212u.

[0056] A first end of the circuit Cu2 (a connection point between the first partial winding 21u3 and the second partial winding 22u3) is connected to the power line 221u, and a second end of the circuit Cu2 (a connection point between the first partial winding 21u4 and the second partial winding 22u4) is connected to the power line 222u.

[0057] A first end of the circuit Cv1 (a connection point between the first partial winding 21v1 and the second partial winding 22v1) is connected to the power line 35v. A second end of the circuit Cv1 (a connection point between the first partial winding 21v2 and the second partial winding 22v2) is connected to the power line 212v.

[0058] A first end of the circuit Cv2 (a connection point between the first partial winding 21v3 and the second partial winding 22v3) is connected to the power line 221v. A second end of the circuit Cv2 (a connection point between the first partial winding 21v4 and the second partial winding 22v4) is connected to the power line 222v.

[0059] A first end of the circuit Cw1 (a connection point between the first partial winding 21w1 and the second partial winding 22w1) is connected to the power line 35w, and a second end of the circuit Cw1 (a connection point between the first partial winding 21w2 and the second partial winding 22w2) is connected to the power line 212w.

[0060] A first end of the circuit Cw2 (a connection point between the first partial winding 21w3 and the second partial winding 22w3) is connected to the power line 221w, and a second end of the circuit Cw2 (a connection point between the first partial winding 21w4 and the second partial winding 22w4) is connected to the power line 222w.

[0061] Furthermore, the second end point of the circuit Cu2, the second end point of the circuit Cv2, and the second end point of the circuit Cw2 are connected to the neutral point 23 (Y connection).

[0062] The winding switching device 100 switches the connection states of the first partial windings 21u1, 21u2, 21u3, 21u4, 21v1, 21v2, 21v3, 21v4, 21w1, 21w2, 21w3, and 21w4 and the second partial windings 22u1, 22u2, 22u3, 22u4, 22v1, 22v2, 22v3, 22v4, 22w1, 22w2, 22w3, and 22w4 for each phase between a first connection state and a second connection state. In the first connection state, the circuits Cu1 and Cu2 are connected in series, the circuits Cv1 and Cv2 are connected in series, and the circuits Cw1 and Cw2 are connected in series. In the second connection state, the circuits Cu1 and Cu2 are connected in parallel, the circuits Cv1 and Cv2 are connected in parallel, and the circuits Cw1 and Cw2 are connected in parallel. The first connection state is a high-torque connection state in which the output torque of the motor 20 is high. The second connection state is a high-rotation connection state in which the rotation speed of the motor 20 is high.

[0063] The winding switching device 100 includes current sensors 101u, 101v, and 101w, zero-cross detection circuits 102u, 102v, and 102w, control circuits 103u, 103v, and 103w, and switching circuits 104u, 104v, and 104w.

[0064] Hereinafter, the first partial windings 21u1, 21u2, 21u3, 21u4, 21v1, 21v2, 21v3, 21v4, 21w1, 21w2, 21w3, and 21w4 will be collectively referred to as the "first partial windings 21," and the second partial windings 22u1, 22u2, 22u3, 22u4, 22v1, 22v2, 22v3, 22v4, 22w1, 22w2, 22w3, and 22w4 will be collectively referred to as the "second partial windings 22."

[0065] The zero-crossing detection circuits 102u, 102v, and 102w detect zero-crossing points of the measured values ​​of the current sensors 101u, 101v, and 101w. In a more specific example, the zero-crossing detection circuits 102u, 102v, and 102w compare the output voltages from the current sensors 101u, 101v, and 101w with zero voltage and detect the time when the output voltages from the current sensors 101u, 101v, and 101w match a reference voltage as the zero-crossing point. The zero voltage is an example of a reference voltage. The reference voltage is a voltage corresponding to the output voltages of the current sensors 101u, 101v, and 101w when the currents flowing through the first partial winding 21 and the second partial winding 22 become zero, and is not limited to zero voltage.

[0066] The switching circuits 104u, 104v, and 104w switch the connection states of the first partial winding 21 and the second partial winding 22 between a first connection state and a second connection state at the timing when the zero-cross detection circuits 102u, 102v, and 102w detect a zero-cross point.

[0067] The switching circuit 104u includes semiconductor relays 111u, 112u, and 113u. The semiconductor relays 111u, 112u, and 113u are, for example, IGBTs or power MOSFETs. The connections of the switching circuits 104v and 104w are similar to those of the switching circuit 104u, and therefore will not be described here.

[0068] The power line 35u is drawn into the winding switching device 100. Inside the winding switching device 100, the power line 35u branches off at a midpoint and is connected to a first terminal of a semiconductor relay 111u. A second terminal of the semiconductor relay 111u is connected to a first terminal of a semiconductor relay 112u. A power line 221u extending from a first end point of the circuit Cu2 is connected to a connection point between the second terminal of the semiconductor relay 111u and the first terminal of the semiconductor relay 112u.

[0069] A second terminal of the semiconductor relay 112u is connected to a first terminal of the semiconductor relay 113u. A power line 212u extending from a second end point of the circuit Cu1 is connected to a connection point between the second terminal of the semiconductor relay 112u and the first terminal of the semiconductor relay 113u. A power line 222u extending from a second end point of the circuit Cu2 is connected to a second terminal of the semiconductor relay 113u.

[0070] When the semiconductor relays 111u and 113u are in the OFF state and the semiconductor relay 112u is in the ON state, the U-phase circuits Cu1 and Cu2 are connected in series. That is, in this case, the first partial windings 21u1, 21u2, 21u3, and 21u4 and the second partial windings 22u1, 22u2, 22u3, and 22u4 are connected in a first connection state. When the semiconductor relays 111u and 113u are in the ON state and the semiconductor relay 112u is in the OFF state, the U-phase circuits Cu1 and Cu2 are connected in series. That is, in this case, the first partial windings 21u1, 21u2, 21u3, and 21u4 and the second partial windings 22u1, 22u2, 22u3, and 22u4 are connected in a second connection state. The same applies to the V-phase and W-phase.

[0071] Signal lines extending from the control circuit 103u are connected to the gate terminals of the semiconductor relays 111u, 112u, and 113u, respectively.

[0072] The power lines 212u, 221u, and 222u extend from the motor 20 and are drawn into the winding switching device 100. A current sensor 101u is attached to the power line 221u. However, the current sensor 101u may be attached to the power lines 35u, 212u, or 222u instead of the power line 221u. The current sensor 101u detects a U-phase current flowing through the power line 221u. The current sensor 101u is, for example, an ACCT that detects only the AC component of the current.

[0073] A signal line extending from the current sensor 101u is connected to the zero-cross detection circuit 102u. A signal line transmitting an output signal of the zero-cross detection circuit 102u (hereinafter referred to as the "zero-cross detection signal") extends from the zero-cross detection circuit 102u to the control circuit 103u. Furthermore, a signal line extending from the control device 50 is connected to the control circuit 103u. The same applies to the V-phase and W-phase.

[0074] The zero-crossing detection circuit 102u detects zero-crossing points of the winding current flowing through the power line 221u measured by the current sensor 101u. The zero-crossing detection circuit 102u is a comparator. For example, the inverting input of the comparator is set to a zero reference voltage, and the output signal of the current sensor 101u is applied to the non-inverting input. As a result, the output of the comparator changes from low to high when the AC signal output from the current sensor 101u crosses the zero reference voltage (zero-crossing point).

[0075] The control circuit 103u receives a switching command signal output from the control device 50 and a zero-cross detection signal output from the zero-cross detection circuit 102u. The control circuit 103u controls the semiconductor relays 111u, 112u, and 113u at the timing when the switching command signal and the zero-cross detection signal are input. For example, when the semiconductor relays 111u and 113u are in the OFF state and the semiconductor relay 112u is in the ON state, the control device 50 switches the semiconductor relays 111u and 113u to the ON state and switches the semiconductor relay 112u to the OFF state at the timing when the switching command signal and the zero-cross detection signal are input to the control device 50. This switches the winding connection state of the motor 20 from the first connection state to the second connection state. When the semiconductor relays 111u and 113u are in the ON state and the semiconductor relay 112u is in the OFF state, the control device 50 switches the semiconductor relays 111u and 113u to the OFF state and switches the semiconductor relay 112u to the ON state at the timing when a switching command signal and a zero-cross detection signal are input to the control device 50. As a result, the winding connection state of the motor 20 switches from the second connection state to the first connection state.

[0076] The control circuit 103u is configured, for example, by an RS flip-flop. Note that the control circuit 103u may be configured by a D flip-flop, a processor, an ASIC (Application Specific Integrated Circuit), or an FPGA (Field Programmable Gate Array). The same applies to the control circuits 103v and 103w.

[0077] The control device 50 is configured with, for example, a processor, a memory, an interface, etc., and controls the winding switching device 100 by executing a control program with the processor. Note that at least a part of the control device 50 may be configured with an ASIC or an FPGA.

[0078] [1-4. Connection State of Windings] Figure 4A is a diagram illustrating an example of a first connection state of the windings in the motor according to the first embodiment, and Figure 4B is a diagram illustrating an example of a second connection state of the windings in the motor according to the first embodiment. In Figures 4A and 4B, the windings surrounded by dashed lines are U-phase windings connected to a power supply (i.e., U-phase windings used to drive motor 20). Note that while only the connection state of the U-phase will be described as a representative example, the connection states of the V-phase and W-phase are similar.

[0079] In the motor 20 according to the first embodiment, the first partial winding 21u1 in the slot Su1 and the first partial winding 21u2 in the slot Su2 adjacent to the slot Su1 are connected in series, and the second partial winding 22u1 in the slot Su1 and the second partial winding 22u2 in the slot Su2 are connected in series. Furthermore, the series circuit of the first partial windings 21u1 and 21u2 and the series circuit of the second partial windings 22u1 and 22u2 are connected in parallel to form a circuit Cu1.

[0080] Similarly, in the motor 20, the first partial winding 21u3 in the slot Su3 is connected in series with the first partial winding 21u4 in the slot Su4 adjacent to the slot Su3, and the second partial winding 22u3 in the slot Su3 is connected in series with the second partial winding 22u4 in the slot Su4. Furthermore, the series circuit of the first partial windings 21u3 and 21u4 and the series circuit of the second partial windings 22u3 and 22u4 are connected in parallel to form a circuit Cu2.

[0081] In the first connection state, the circuits Cu1 and Cu2 are connected in series as shown in Fig. 4A. In the second connection state, the circuits Cu1 and Cu2 are connected in parallel as shown in Fig. 4B.

[0082] FIG. 5 is a circuit diagram showing an example of the connection relationship of the U-phase windings in the motor according to the first embodiment.

[0083] 5, the induced voltages in the first partial winding 21u1 and the second partial winding 22u1 in the slot Su1 and the first partial winding 21u1 and the second partial winding 22u1 in the slot Su3 have the same phase. The induced voltages in the first partial winding 21u2 and the second partial winding 22u2 in the slot Su2 and the first partial winding 21u4 and the second partial winding 22u4 in the slot Su4 have the same phase. The induced voltages in the first partial winding 21u1 and the second partial winding 22u1 in the slot Su1 and the first partial winding 21u2 and the second partial winding 22u2 in the slot Su2 adjacent to the slot Su1 have different phases. The induced voltage phase differs between the first partial winding 21u3 and the second partial winding 22u3 in the slot Su3 and the first partial winding 21u4 and the second partial winding 22u4 in the slot Su4 adjacent to the slot Su3.

[0084] In the first connection state in which the circuits Cu1 and Cu2 are connected in series, the first partial winding 21u1 and the second partial winding 22u1 in the slot Su1 are connected in parallel, the first partial winding 21u2 and the second partial winding 22u2 in the slot Su2 are connected in parallel, the first partial winding 21u3 and the second partial winding 22u3 in the slot Su3 are connected in parallel, and the first partial winding 21u4 and the second partial winding 22u4 in the slot Su4 are connected in parallel. That is, the induced voltage phases are the same between the parallel elements (partial windings).

[0085] On the other hand, in the second connection state in which the circuits Cu1 and Cu2 are connected in parallel, the first partial winding 21u1 and the second partial winding 22u1 in the slot Su1 and the first partial winding 21u3 and the second partial winding 22u3 in the slot Su3, which is 180° away from the slot Su1, are connected in parallel, and the first partial winding 21u2 and the second partial winding 22u2 in the slot Su2 and the first partial winding 21u4 and the second partial winding 22u4 in the slot Su4, which is 180° away from the slot Su2, are connected in parallel (see FIG. 4B ). Therefore, even in the second connection state, the induced voltage phases are the same between the parallel elements (partial windings). This prevents circulating currents between parallel elements due to differences in induced voltage phase, as well as the resulting sudden changes in torque and burnout of the windings and semiconductor relays in the switching circuit. In a motor with one winding per slot, it is possible to construct a motor with characteristics similar to those of windings in the same phase slots connected in parallel.

[0086] 6 is a circuit diagram showing an example of the configuration of a winding switching device according to the second embodiment. In a motor 20A according to the second embodiment, a parallel circuit (first parallel circuit) of the first partial winding 21u1 in the slot Su1 and the second partial winding 22u1 in the slot Su1 and a parallel circuit (second parallel circuit) of the first partial winding 21u2 in the slot Su2 and the second partial winding 22u2 in the slot Su2 are connected in series to form a circuit Cu1A (third circuit).

[0087] A parallel circuit (third parallel circuit) of the first partial winding 21u3 in slot Su3 and the second partial winding 22u3 in slot Su3, and a parallel circuit (fourth parallel circuit) of the first partial winding 21u4 in slot Su4 and the second partial winding 22u4 in slot Su4 are connected in series to form a circuit Cu2A (fourth circuit).

[0088] A parallel circuit (first parallel circuit) of the first partial winding 21v1 in the slot Sv1 and the second partial winding 22v1 in the slot Sv1, and a parallel circuit (second parallel circuit) of the first partial winding 21v2 in the slot Sv2 and the second partial winding 22v2 in the slot Sv2 are connected in series to form a circuit Cv1A (third circuit).

[0089] A parallel circuit (third parallel circuit) of the first partial winding 21v3 in the slot Sv3 and the second partial winding 22v3 in the slot Sv3, and a parallel circuit (fourth parallel circuit) of the first partial winding 21v4 in the slot Sv4 and the second partial winding 22v4 in the slot Sv4 are connected in series to form a circuit Cv2A (fourth circuit).

[0090] A parallel circuit (first parallel circuit) of the first partial winding 21w1 in the slot Sw1 and the second partial winding 22w1 in the slot Sw1, and a parallel circuit (second parallel circuit) of the first partial winding 21w2 in the slot Sw2 and the second partial winding 22w2 in the slot Sw2 are connected in series to form a circuit Cw1A (third circuit).

[0091] A parallel circuit (third parallel circuit) of the first partial winding 21w3 in the slot Sw3 and the second partial winding 22w3 in the slot Sw3, and a parallel circuit (fourth parallel circuit) of the first partial winding 21w4 in the slot Sw4 and the second partial winding 22w4 in the slot Sw4 are connected in series to form a circuit Cw2A (fourth circuit).

[0092] A first end of the circuit Cu1A (a connection point between the first partial winding 21u1 and the second partial winding 22u1) is connected to the power line 35u, and a second end of the circuit Cu1A (a connection point between the first partial winding 21u2 and the second partial winding 22u2) is connected to the power line 212u.

[0093] A first end of the circuit Cu2A (a connection point between the first partial winding 21u3 and the second partial winding 22u3) is connected to the power line 221u, and a second end of the circuit Cu2A (a connection point between the first partial winding 21u4 and the second partial winding 22u4) is connected to the power line 222u.

[0094] A first end of the circuit Cv1A (a connection point between the first partial winding 21v1 and the second partial winding 22v1) is connected to the power line 35v. A second end of the circuit Cv1A (a connection point between the first partial winding 21v2 and the second partial winding 22v2) is connected to the power line 212v.

[0095] A first end of the circuit Cv2A (a connection point between the first partial winding 21v3 and the second partial winding 22v3) is connected to the power line 221v. A second end of the circuit Cv2A (a connection point between the first partial winding 21v4 and the second partial winding 22v4) is connected to the power line 222v.

[0096] A first end of the circuit Cw1A (a connection point between the first partial winding 21w1 and the second partial winding 22w1) is connected to the power line 35w, and a second end of the circuit Cw1A (a connection point between the first partial winding 21w2 and the second partial winding 22w2) is connected to the power line 212w.

[0097] A first end of the circuit Cw2A (a connection point between the first partial winding 21w3 and the second partial winding 22w3) is connected to the power line 221w, and a second end of the circuit Cw2A (a connection point between the first partial winding 21w4 and the second partial winding 22w4) is connected to the power line 222w.

[0098] Furthermore, the second end point of the circuit Cu2A, the second end point of the circuit Cv2A, and the second end point of the circuit Cw2A are connected to the neutral point 23 (Y connection).

[0099] The winding switching device 100 switches the connection states of the first partial windings 21u1, 21u2, 21u3, 21u4, 21v1, 21v2, 21v3, 21v4, 21w1, 21w2, 21w3, and 21w4 and the second partial windings 22u1, 22u2, 22u3, 22u4, 22v1, 22v2, 22v3, 22v4, 22w1, 22w2, 22w3, and 22w4 for each phase between a first connection state and a second connection state. In the first connection state, the circuits Cu1A and Cu2A are connected in series, the circuits Cv1A and Cv2A are connected in series, and the circuits Cw1A and Cw2A are connected in series. In the second connection state, the circuits Cu1A and Cu2A are connected in parallel, the circuits Cv1A and Cv2A are connected in parallel, and the circuits Cw1A and Cw2A are connected in parallel. The first connection state is a high-torque connection state in which the output torque of the motor 20 is high. The second connection state is a high-rotation connection state in which the rotation speed of the motor 20 is high.

[0100] Other configurations of the motor 20A and the winding switching device 100 according to the second embodiment are similar to those of the motor 20 and the winding switching device 100 according to the first embodiment, and therefore description thereof will be omitted.

[0101] Fig. 7A is a diagram illustrating an example of a first connection state of windings in a motor according to the second embodiment, and Fig. 7B is a diagram illustrating an example of a second connection state of windings in a motor according to the second embodiment. In Fig. 7A and Fig. 7B, the windings surrounded by dashed lines are U-phase windings connected to a power supply (i.e., U-phase windings used to drive motor 20). Note that while only the connection state of the U-phase will be described as a representative example, the connection states of the V-phase and W-phase are similar.

[0102] In the motor 20A according to the second embodiment, the first partial winding 21u1 and the second partial winding 22u1 in the slot Su1 are connected in parallel, and the first partial winding 21u2 and the second partial winding 22u2 in the slot Su2 are connected in parallel. Furthermore, a parallel circuit of the first partial winding 21u1 and the second partial winding 22u1 and a parallel circuit of the first partial winding 21u2 and the second partial winding 22u2 are connected in series to form a circuit Cu1A.

[0103] Similarly, in the motor 20A, the first partial winding 21u3 and the second partial winding 22u3 in the slot Su3 are connected in parallel, and the first partial winding 21u4 and the second partial winding 22u4 in the slot Su4 are connected in parallel. Furthermore, a parallel circuit of the first partial winding 21u3 and the second partial winding 22u3 and a parallel circuit of the first partial winding 21u4 and the second partial winding 22u4 are connected in series to form a circuit Cu2A.

[0104] In the first connection state, the circuits Cu1A and Cu2A are connected in series as shown in Fig. 7A. In the second connection state, the circuits Cu1A and Cu2A are connected in parallel as shown in Fig. 7B.

[0105] FIG. 8 is a circuit diagram showing an example of the connection relationship of the U-phase windings in the motor according to the second embodiment.

[0106] 8, the induced voltages in the first partial winding 21u1 and the second partial winding 22u1 in the slot Su1 and the first partial winding 21u1 and the second partial winding 22u1 in the slot Su3 have the same phase. The induced voltages in the first partial winding 21u2 and the second partial winding 22u2 in the slot Su2 and the first partial winding 21u4 and the second partial winding 22u4 in the slot Su4 have the same phase. The induced voltages in the first partial winding 21u1 and the second partial winding 22u1 in the slot Su1 and the first partial winding 21u2 and the second partial winding 22u2 in the slot Su2 adjacent to the slot Su1 have different phases. The induced voltage phase differs between the first partial winding 21u3 and the second partial winding 22u3 in the slot Su3 and the first partial winding 21u4 and the second partial winding 22u4 in the slot Su4 adjacent to the slot Su3.

[0107] In the first connection state in which the circuit Cu1A and the circuit Cu2A are connected in series, the first partial winding 21u1 and the second partial winding 22u1 in the slot Su1 are connected in parallel, the first partial winding 21u2 and the second partial winding 22u2 in the slot Su2 are connected in parallel, the first partial winding 21u3 and the second partial winding 22u3 in the slot Su3 are connected in parallel, and the first partial winding 21u4 and the second partial winding 22u4 in the slot Su4 are connected in parallel. That is, the induced voltage phases are the same between the parallel elements (partial windings).

[0108] On the other hand, in the second connection state in which the circuits Cu1 and Cu2 are connected in parallel, the first partial winding 21u1 and the second partial winding 22u1 in the slot Su1 and the first partial winding 21u3 and the second partial winding 22u3 in the slot Su3, which is 180° away from the slot Su1, are connected in parallel, and the first partial winding 21u2 and the second partial winding 22u2 in the slot Su2 and the first partial winding 21u4 and the second partial winding 22u4 in the slot Su4, which is 180° away from the slot Su2, are connected in parallel (see FIG. 7B ). Therefore, even in the second connection state, the induced voltage phases are the same between the parallel elements (partial windings). This prevents circulating currents between parallel elements due to differences in induced voltage phase, as well as the resulting sudden changes in torque and burnout of the windings and semiconductor relays in the switching circuit. In a motor with one winding per slot, it is possible to construct a motor with characteristics similar to those of windings in the same phase slots connected in parallel.

[0109] [3. Other Modifications] The configuration of the motor according to the above-described embodiment is merely an example and is not intended to be limiting. For example, in a permanent magnet synchronous motor with a number of poles and slots other than 10 poles and 12 slots, the winding may be divided in each slot. Furthermore, the number of divisions of the winding in each slot does not have to be two. For example, the winding in each slot may be divided into three or more partial windings. For example, if the winding in a slot is divided into a first partial winding, a second partial winding, and a third partial winding, the first partial winding, the second partial winding, and the third partial winding are arranged in parallel.

[0110] [4. Supplementary Note] The embodiments disclosed herein are illustrative in all respects and are not restrictive. The scope of the present invention is defined by the claims, not the above-described embodiments, and includes meanings equivalent to the claims and all modifications within the scope thereof.

[0111] 10 Winding switching system 20 Motor 21u1, 21u2, 21u3, 21u4, 21v1, 21v2, 21v3, 21v4, 21w1, 21w2, 21w3, 21w4, 21 First partial winding 22u1, 22u2, 22u3, 22u4, 22v1, 22v2, 22v3, 22v4, 22w1, 22w2, 22w3, 22w4, 22 Second partial winding 23 Neutral point 210 Stator 210Y Yoke 210Tu1, 210Tu2, 210Tv1, 210Tv2, 210Tw1, 210Tw2, 210Tu3, 210Tu4, 210Tv3, 210Tv4, 210Tw3, 210Tw4, 210T Teeth 220 Rotor 220M Permanent magnet 25 Power line 30 Power converter 31u, 32u, 31v, 32v, 31w, 32w Switch 33u, 33v, 33w Current sensor 35u, 35v, 35w Power line 40 Battery 50 Control device 100 Winding switching device 101u, 101v, 101w Current sensor 102u, 102v, 102w Zero cross detection circuit 103u, 103v, 103w Control circuit 104u, 104v, 104w Switching circuit 111u, 112u, 113u, 111v, 112v, 113v, 111w, 112w, 113w Semiconductor relays 212u, 221u, 222u, 212v, 221v, 222v, 212w, 221w, 222w Power lines Cu1, Cu2, Cv1, Cv2, Cw1, Cw2 Circuit 20A Motor Cu1A, Cu2A, Cv1A, Cv2A, Cw1A, Cw2A Circuit

Claims

1. A polyphase AC motor comprising: a plurality of first partial windings wound around a plurality of teeth, respectively; and a plurality of second partial windings wound around the plurality of teeth, respectively; wherein the first partial windings and the second partial windings wound around the same teeth are connected in parallel.

2. A polyphase AC motor as set forth in claim 1, wherein a first series circuit in which the first partial winding wound on the first tooth and the first partial winding wound on the second tooth are connected in series, and a second series circuit in which the second partial winding wound on the first tooth and the second partial winding wound on the second tooth are connected in series, are connected in parallel in the same phase.

3. A polyphase AC motor as set forth in claim 2, wherein a third series circuit in which the first partial winding wound around the third tooth and the first partial winding wound around the fourth tooth are connected in series, and a fourth series circuit in which the second partial winding wound around the third tooth and the second partial winding wound around the fourth tooth are connected in series, are connected in parallel in the same phase as the first series circuit and the second series circuit.

4. The polyphase AC motor according to claim 3, wherein the first series circuit, the second series circuit, the third series circuit, and the fourth series circuit can be connected in parallel.

5. A polyphase AC motor according to claim 4, configured to be switchable between a first connection state in which a first circuit in which the first series circuit and the second series circuit are connected in parallel and a second circuit in which the third series circuit and the fourth series circuit are connected in parallel are connected in series, and a second connection state in which the first circuit and the second circuit are connected in parallel.

6. A polyphase AC motor as claimed in claim 1, in which a first parallel circuit in which the first partial winding wound around a first tooth and the second partial winding wound around the first tooth are connected in parallel, and a second parallel circuit in which the first partial winding wound around a second tooth and the second partial winding wound around the second tooth are connected in parallel, are connected in series in the same phase.

7. A polyphase AC motor as set forth in claim 6, wherein a third parallel circuit in which the first partial winding wound around a third tooth and the second partial winding wound around the third tooth are connected in parallel, and a fourth parallel circuit in which the first partial winding wound around a fourth tooth and the second partial winding wound around the fourth tooth are connected in parallel, are connected in series in the same phase as the first parallel circuit and the second parallel circuit.

8. The polyphase AC motor according to claim 7, wherein the first parallel circuit, the second parallel circuit, the third parallel circuit, and the fourth parallel circuit can be connected in series.

9. The polyphase AC motor according to claim 8, configured to be switchable between a third connection state in which a third circuit in which the first parallel circuit and the second parallel circuit are connected in series and a fourth circuit in which the third parallel circuit and the fourth parallel circuit are connected in series, and a fourth connection state in which the third circuit and the fourth circuit are connected in parallel.

10. A polyphase AC motor as claimed in any one of claims 2 to 9, wherein a first phase difference between a first stator magnetic field formed by the first partial winding and the second partial winding wound around the first teeth and a rotor magnetic field formed by the rotor is different from a second phase difference between a second stator magnetic field formed by the first partial winding and the second partial winding wound around the second teeth and a rotor magnetic field formed by the rotor.

11. A polyphase AC motor as set forth in claim 10, wherein a third phase difference between a third stator magnetic field formed by the first partial winding and the second partial winding wound around a third tooth and a rotor magnetic field formed by the rotor is different from a fourth phase difference between a fourth stator magnetic field formed by the first partial winding and the second partial winding wound around a fourth tooth and a rotor magnetic field formed by the rotor.

12. The polyphase AC motor according to claim 11, wherein the first phase difference and the third phase difference are the same, and the second phase difference and the fourth phase difference are the same.

13. A winding switching system comprising: a polyphase AC motor capable of switching the connection state of a plurality of windings between a first connection state and a second connection state; a power converter that converts power output from a power source into AC power and supplies the AC power to the AC motor; and a winding switching device for switching the connection state of the plurality of windings, wherein the polyphase AC motor includes a plurality of first partial windings wound around each of a plurality of teeth, and a plurality of second partial windings wound around each of the plurality of teeth, and the first partial winding and the second partial winding wound around the same tooth are connected in parallel.

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